NO. 3 (1921) LACQUERING OF CANS 26I 



Stout layer of oil-varnish. It is possible that with this thicker 

 initial coating, a single coating may suffice, but a second applica- 

 tion is invariable at the Chaliyam cannery. One good result from 

 a thick and thorough coating is that the varnish seals up any very 

 slight pin-hole or interstice in the joints of the can, and since, 

 ex hypothesis the coating will resist boiling water, the hermeticity 

 of the seal is more completely assured. • 



If plain boiled oil is used (without the addition of a gum) as a 

 coating, it should have been so boiled as to be of very thick con- 

 sistency ; it should then be thinned with turps to allow of ready 

 application ; the turps rapidly evaporates leaving an elastic 

 coating of solid oil. But a resinous varnish is mostly used. 



The canners may try the dilution, if any, which suits them, viz., 

 either a thinning with turps, or a thickening with old Iwilcd linseed 

 oil, or the commercial article as it is. 



It is not necessary to add any solid materials to the varnish 

 which would make it into an " enamel"; such addition would add 

 expense and difficulty, and some materials might even be dele- 

 terious. 



7, Point 3 — Stoving. — Ordinarily, lacquer is simply allowed to 

 dry, but, for at least two reasons, stoving, that is, drying in a stove 

 or heated chamber at a considerable temperature, is desirable; viz., 

 (i) it hastens the process, (2) it so hardens the lacquer that it will 

 subsequently stand even moist heat, and it is found that lacquer 

 resists destructive influences all the better if stoved (within 

 reasonable limits of course) at a comparatively high temperature 

 and for a long period. 



This temperature, for our canning purposes, may be taken as 

 from 250° to 300° F. ; it must not exceed 300° F. since the goods to 

 be lacquered are soldered cans, and ordinary good solder softens 

 at 320° F., so that the cans would fall to pieces if the temperature 

 appreciably exceeded that degree. The time, usually several 

 hours, depends upon temperature and experience ; the lower the 

 temperature the longer the time; the process should result in a 

 hard coating which can barely be scratched, and certainly must 

 not be removable by the finger-nail. 



8. Point 3 — The stove. — This is simply a chamber or other recep- 

 tacle which can be heated so that a moderate equable temperature 

 may be continuously maintained ; it must be so constructed that 

 each part is equally heated ; the temperature should not materially 



